Doxazosin is an alpha-1 blocker used for hypertension. Alpha blockers work by overcoming the vasoconstricting properties of the stress neurotransmitter noradrenaline (norepinephrine). Essentially noradrenaline is the braking system to keep your erections and other “systems of relaxation” from going on forever. Unfortunately, in some men under stress and a Western lifestyle, the brakes can be on virtually all the time and this can negatively impact sexual function. Doxazosin is also prescribed for BPH (enlarged prostate) and works in a similar way on the prostate by relaxing smooth muscle tissue.
NOTE: Terazosin is another similar alpha-1 blocker that has a similar profile, i.e. is used to treat hypertension and BPH. It does not, however, have any erectile dysfunction studies under its belt yet.
Many experts feel that alpha blockers are understudied and underutilized tool in the arsenal against erectile dysfunction, because they can work miraculously for so many men. We give coverage to one other alpha blocker, which works on both the alpha-1 and alpha-2 receptors, and holds a great deal of promise for some men. See my link on Erectile Dysfunction and Phentolamine for more information. However, this medication is not yet approved in most countries as we will discuss below.
CAUTION: All the alpha blockers should only be used under a doctor’s supervision, because they 1) interact very negatively with certain medications, 2) can have very serious side effects and 3) can cause priapism, an erection that does not go away and can damage the penis permanently. See my link on Common Causes of Priapism for more information on the latter. If you ever have an erection that will no go away after an hour or two, go to the E.R. immediately.
There are many reports that this blood-pressure lowering drug (an alpha-blocker) enhances the effects of PDE5i. So, though I generally have healthy blood-pressure, I persuaded my doctor, in 2008, to prescribe me daily 2mg doxazosin. (The maximum advised doxazosin dose is 16mg.) It acts as a vasodilator, and so the theoretical erection-enhancing effect is obvious.
The International Journal of Impotence Research reported in 2002 on a trial conducted by the University Hospital Genoa which investigated the efficacy and safety of sildenafil in combination with doxazosin for the treatment of non-organic erectile dysfunction in men who did not respond to sildenafil alone. 28 patients were divided in two groups: 14 were treated with doxazosin (4 mg daily) and sildenafil (100 mg before sex); the other 14 patients received sildenafil and placebo. Of the 14 patients treated with doxazosin and sildenafil, 11 showed an average increase in IIEF-EF score from 12 at baseline to 22 after 60 days. (That s much more of an increase than is generally provided by the LI-ESWT. And I don t believe it.) Only one patient in the placebo group recorded a significant increase. Blood pressure did not show significant alterations.
A Korean trial concluded in 2012 that we believe that the combination of a PDE5 inhibitor with doxazosin could be a pharmacologic strategy for simultaneously treating ED and its comorbidities and increasing response rates to PDE5 inhibitors .
Pfizer states caution is advised when PDE5 inhibitors are co-administered with alpha-blockers as the hypotensive effects of alpha-blockers and PDE5i can combine. They advise that patients already taking PDE5i, should initiate alpha-blocker therapy at the lowest dose ; and if already on alpha-blockers initiate Viagra at the lowest dose. The Levitra package leaflet offers the same advice. The Cialis package leaflet advises that you tell your doctor if you take alpha blockers.
I have checked my blood pressure when first on this combination of drugs, and it was around its usual 120/80.
Doxazosin initially, in 2008, made me feel a bit odd, slightly dizzy, but this effect disappeared after a few weeks. My doctor, without referring to PDE5i, suggested I start on half a tablet, to avoid the worst of these side effects, before taking the whole 2mg. I did that, and I thought did detect a positive effect on erections. After a couple of years I reduced the dose to 1mg a day, and then stopped altogether. Between June 2012 and January 2013 I had no doxazosin. I can t recall why I stopped doxazosin, I think I started to take the benefit for granted, and I then I just forgot about it. (And my blood pressure rose slightly around 125/85.)
Reflecting on doxazosin in early January 2013 I recalled the reliability of my erections reduced with the reduced doxazosin intake, so I restarted daily 2mg doxazosin on 20th January 2013. After a few months of noticing no improvement I reduced the dose to 1mg a day.
A private prescription allows you to buy a month s supply of 2mg Doxazosin for 1; much less than the 7.65 NHS charge.
NOTE: The most common side effect is probably dizzines. Other hypoglycemic-like symptoms can occur as well.